Insulator heating circuit



Aug. 15, 1933, A. N. CROWDER INSULATOR HEATING CIRCUIT Filed Jan. 8,1932 2 Sheets-Sheet l g. 15, 1933. ANl COWDER 1,922,125

IJNSULATOR HEATING CIRCUIT Filed Jan. 8, 1952 2 Sheets-Sheet 2 4 di? a lU 2@ l Ja j L5 i y' `l Il LL@ ff@ j Patented Aug. l5, 1933 PATENToFF-ica v 1,922,125 INsULA'roR HEATING ontcurr Alexander N. Crowder,Bound Brook, N. J., as-

signor to Research Corporation, New York, N. Y., a Corporation of NewYork Application January s, 1932. seriai No; 585,608

l Claims.

This invention relates to a method and device for heating electricalinsulators. It is particularly adapted for use in connection Withanelectrical system comprising a low voltage circuit whichincludesresistance and other control units coupled through a step-uptransformer to a high voltage circuit which includes elements forproducing discharges in gases and high voltage insulators exposed tosaidgases.

The principal object of the invention is the e'icient utilization of theenergy dissipated by the current-regulating devices. This object isaccomplished by associating with insulators in the high voltage circuitthe heat-generating regulating means in the low-voltage circuit.

The invention may be illustrated by describing its application to theart of electrical precipitation. In electrical precipitatorinstallations it is common practice to include a considerable amount ofso-called ballasting resistance in the low voltage side of the circuitfor the purpose of damping the current surges that are set up whenarc-overs occur in the high voltage side of the circuit between theelectrodes within the precipitator. The use of such resistance alsotends to prevent a condition of resonance in the system which mightotherwise f exist due to the inductance and capacity present in such anelectrical system. Sometimes it is found necessary to introduce suicientresistance to reduce the voltage available at the low voltage, terminalsof the transformer to one-half that supplied by the power lines. Attimes of arc-over when heavy rushes of current take place, the drop involtage may be even greater than 50%.

When the amount of resistance provided for the purpose of controllingthe electrical conditions in the system is sufcient to bring about anappreciable drop in voltage, considerable of the energy consumed in thesystem consists oi 12R loss in the resistance units and the usualpractice is to dissipate this energy as heat into the surrounding air.rlhis invention is directed toward the economical utilization of thisenergy.

In electrical precipitators used with gases containing moist andconducting particles, it has been found to be good practice to heat thesurface of the high voltage insulators riuhere exposed to the gases toprevent the deposition of conducting particles on this surface. Theinsulators are commonly heated by placing chambers around them andheating the gas in the chamberswith steam coils. In the presentinvention, advantage is taken of the fact that (Clo 18S-7) v lelectrical energy is being dissipated in the form of heat in the lowVoltage side of the precipita-- tor circuit and the resistance unitsgiving oi this heat are placed within the high voltage insulatorchambers or within the shells of the insulators themselves, or otherwiseassociated in heal'. transfer relations with the insulators. Thus thesurface of the insulators is maintained at temperatures above the dewpoint of the gases being cleaned, or otherwise treated.

The invention will be described, by way of example, with reference tothe accompanyingr iigures, wherein:

Figure l shows in elevation, partly in section. an assembly of highvoltage insulators, including a bushing with electrical heatingelements;

Figure 2 is a lplan View through section 2 2 of Figure 1;

Figure 3 shows in side elevation a supporting insulator, such as areused in Aelectrical precipitators, with an electrical heating unit;

Figure 4.- shows diagrammatically the manner in which insulators such asthose shown in Figures 1, 2 and 3, when used in an electricalprecipitatorcan be heated in accordance with the invention.

In Figures l and 2, 1 is an insulating bushing which covers in more orless gas-tight manner the opening 2 in plate 3, but in which there is asmall opening 5 through which a supporting rod l passes to make possiblethe suspension of the framework below the plate, represented by member7, from member 6 above the plate.

Member 6 is supported by insulators 8. The inside of bushing 1 is heatedby electrical heaters 9 of the air immersion type. Such an assembly ofinsulators is useful in apparatus for the electrical treatment of gases,and when so considering it, plate 3 represents the top plate of a casingholding the gas to be treated and member 7 represents the framework fromwhich electrodes may be hung in the manner well known to those versed inthe art. Connections 10 and 1l are a part of an electrical supplycircuit to be described later.

Figure 3 illustrates the use of a supporting insulator in apparatus forthe removal of suspended particles from gases in which the insulator isnot fully protected from the gas passing through the apparatus andrequires heating to prevent the deposition of conducting material uponit. The insulator 12 supports the high voltage busbar l5 from whichdischarge electrodes, such as lamentary member 23, are suspended withingrounded collecting electrodes,

such as pipe 22. A sleeve 17 is placed over the bus bar 15, where itpasses through the shell 16 of the precipitator chamber 16 and a torusring 18 covers the edge of the hole in shell 16' so that the annularopening 14, defined by said sleeve and torus ring, is free from edgeswhich would permit disruptive spark-overs at relatively low voltages.Because of this freedom from sharp edges, the annular opening 14 can bequite narrow and the movement of gas into and out of the insulator box13 is not great. It is often advisable, however, to heat the gascontained in the insulator box to provide against the deposition of dustin a moist, conducting condition or condensed vapors, on the surfaces ofthe insulator. The insulator 12 and the gas immediately surrounding itis heated with an electricalresistance unit 19, made up in helical formand maintained in position around the insulator by fastenings 20 whichproject out from the sides of the insulator box 13. Heating unit 19 issupplied with electric current through conductors 21 which are shownentering the bottom of the insulator box.

In Figure 4, outline 33 indicates in plan view an electricalprecipitator for the removal of suspended particles from gases. Theinsulation for this precipitator is similar to that shown in Figs. 1 and2. 'Ihe supporting insulators are represented by 28 and gas-tightbushings 3l are shown around rods 24. The resistance units 27 which arefor the purpose of heating bushings 31 are connected by insulated wires29 and 30 to conductors 25 and 26, respectively. As shown, tworesistance units are connected in series by connector 30 'for theheating of a single bushing.

Current to heat the resistance units or heaters 27 is secured from thepower supply lines through connections 41 and 42. It can be supplieddirectly to the resistance units through switch 34, or switch 35 can beused to connect the resistance units 31 in series with variableresistance 36 and the low tension winding of transformer 37. The formerconnection can be used when the installation is being made ready for thetreatment of gases and before the transformer and rectifier are placedin service. With the connection through switch 34, full voltage isimpressed across each two resistance units, which impresses half "linevoltage across each unit. This is a desirable condition when no gas ispassing toassist in heating'the bushings 31 and all the heat must besecured from the electrical heaters 27. When the bushings are heated toa satisfactory working temperature, the gas may be allowed to flowthrough the precipitator and voltage is impressed on the high voltageelectrode system of the precipitator. n

To energize the high voltage electrode system, switch 34 is opened andswitch 35 is closed. With switch 35 closed, current flows throughtransformer 37, the current from the high voltage winding of thetransformer is rectified by translating device 38 and the resultingunidirectional current is supplied to the high voltage electrodes byconductor 39 which is connected to one of the supporting rods 24.

It is evident that the voltage available across the resistance units l27within the bushings 31 is less when the transformer 37 and resistance 36is included in the circuit. This is a desirable condition because lessheat is required to maintain the bushings at the proper temperature thanis required to bring them up to that temperature; and furthermore, asmost gases which require cleaning or conditioning are above atmospherictemperatures, the gases furnislran additional source of heat as soon asthey are passed through the precipitator to be cleaned.

Variations in the above circuits will be apparent to those familiar withthe operation of electrical precipitation units. The voltage to beimpressed on the low-voltage Winding of the transformer can be alteredby use of the auxiliary variable resistance 36. Also, to giveflexibility to the values of the high voltage current, several taps canbe made to the low voltage winding in a manner well known to transformerengineers. Also, the resistor units within the insulator bushings can beconnected up variously in series and in parallel so that the voltageacross an individual resistance unit can be changed by changing theconnections to these units.

The particular arrangements shown in the drawings and described aboveare merely examples of the principle of the invention, and it will beseen that the invention broadly comprises the lheating of high voltageinsulators in a system containing high voltage and low voltage circuitsby associating heat-generating regulating means in the low voltagecircuit in heat transfer relation with the high voltage insulators, theterm insulators being used broadly to denote devices or elements forpreventing undesired leakage of current from electrical conductors.

I claim:

1. Apparatus for the treatment of gases with high potential electricaldischarges comprising a low voltage circuit, a transformer, a highvoltage circuit, insulators in said high voltage circuit andheat-generating means in said low voltage circuit for regulating thecurrent charac` teristics of the system, said means being associated inheat transfer relation with said insulators.

2. Apparatus for the treatment of gases with high potential electricaldischarges comprising a low voltage circuit, a transformer, a highvoltage circuit, insulators in said high .voltage circuit and resistanceelements in said low voltage circuit for regulating the currentcharacteristics of the system, said elements being associated in heattransfer relation with said insulators.

3. Apparatus for the treatment of gases with high potential electricaldischarges comprising a low voltage circuit, a transformer, a highvoltage circuit, insulators in association with the high voltageconductors of said high voltage circuit, and resistance regulativeelements in said low voltage circuit positioned in heat transferrelation to said insulators.

4. Apparatus for the treatment of gases with high potential electricaldischarges comprising a low voltage circuit, a transformer, a highvoltage circuit, insulators in association with the high voltageconductors of said high voltage circuit, resistance regulative elementsin said low voltage circuit positioned in proximity to said insulators,and current switching means adapted to connect a source of low voltagesupply with said regulative elements either directly or in series withsaid transformer.

ALEXANDER N. CROWDER.

